/*
 *  Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 */

#ifndef WTF_PassRefPtr_h
#define WTF_PassRefPtr_h

#include "wtf/Assertions.h"
#include "wtf/RawPtr.h"
#include "wtf/TypeTraits.h"

namespace WTF {

template <typename T> class RefPtr;
template <typename T> class PassRefPtr;
template <typename T> PassRefPtr<T> adoptRef(T*);

inline void adopted(const void*) {}

// requireAdoption() is not overloaded for WTF::RefCounted, which has a built-in
// assumption that adoption is required. requireAdoption() is for bootstrapping
// alternate reference count classes that are compatible with ReftPtr/PassRefPtr
// but cannot have adoption checks enabled by default, such as skia's
// SkRefCnt. The purpose of requireAdoption() is to enable adoption checks only
// once it is known that the object will be used with RefPtr/PassRefPtr.
inline void requireAdoption(const void*) {}

template <typename T> ALWAYS_INLINE void refIfNotNull(T* ptr)
{
    if (LIKELY(ptr != 0)) {
        requireAdoption(ptr);
        ptr->ref();
    }
}

template <typename T> ALWAYS_INLINE void derefIfNotNull(T* ptr)
{
    if (LIKELY(ptr != 0))
        ptr->deref();
}

template <typename T> class PassRefPtr {
public:
    PassRefPtr() : m_ptr(nullptr) {}
    PassRefPtr(std::nullptr_t) : m_ptr(nullptr) {}
    PassRefPtr(T* ptr) : m_ptr(ptr) { refIfNotNull(ptr); }
    template <typename U> PassRefPtr(const RawPtr<U>& ptr, EnsurePtrConvertibleArgDecl(U, T)) : m_ptr(ptr.get()) { refIfNotNull(m_ptr); }
    explicit PassRefPtr(T& ptr) : m_ptr(&ptr) { m_ptr->ref(); }
    // It somewhat breaks the type system to allow transfer of ownership out of
    // a const PassRefPtr. However, it makes it much easier to work with
    // PassRefPtr temporaries, and we don't have a need to use real const
    // PassRefPtrs anyway.
    PassRefPtr(const PassRefPtr& o) : m_ptr(o.leakRef()) {}
    template <typename U> PassRefPtr(const PassRefPtr<U>& o, EnsurePtrConvertibleArgDecl(U, T)) : m_ptr(o.leakRef()) {}

    ALWAYS_INLINE ~PassRefPtr() { derefIfNotNull(m_ptr); }

    template <typename U> PassRefPtr(const RefPtr<U>&, EnsurePtrConvertibleArgDecl(U, T));

    T* get() const { return m_ptr; }

    T* leakRef() const WARN_UNUSED_RETURN;

    T& operator*() const { return *m_ptr; }
    T* operator->() const { return m_ptr; }

    bool operator!() const { return !m_ptr; }

    // This conversion operator allows implicit conversion to bool but not to
    // other integer types.
    typedef T* (PassRefPtr::*UnspecifiedBoolType);
    operator UnspecifiedBoolType() const { return m_ptr ? &PassRefPtr::m_ptr : 0; }

    friend PassRefPtr adoptRef<T>(T*);

private:
    enum AdoptRefTag { AdoptRef };
    PassRefPtr(T* ptr, AdoptRefTag) : m_ptr(ptr) {}

    PassRefPtr& operator=(const PassRefPtr&)
    {
        static_assert(!sizeof(T*), "PassRefPtr should never be assigned to");
        return *this;
    }

    mutable T* m_ptr;
};

template <typename T>
template <typename U> inline PassRefPtr<T>::PassRefPtr(const RefPtr<U>& o, EnsurePtrConvertibleArgDefn(U, T))
    : m_ptr(o.get())
{
    T* ptr = m_ptr;
    refIfNotNull(ptr);
}

template <typename T> inline T* PassRefPtr<T>::leakRef() const
{
    T* ptr = m_ptr;
    m_ptr = nullptr;
    return ptr;
}

template <typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, const PassRefPtr<U>& b)
{
    return a.get() == b.get();
}

template <typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, const RefPtr<U>& b)
{
    return a.get() == b.get();
}

template <typename T, typename U> inline bool operator==(const RefPtr<T>& a, const PassRefPtr<U>& b)
{
    return a.get() == b.get();
}

template <typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, U* b)
{
    return a.get() == b;
}

template <typename T, typename U> inline bool operator==(T* a, const PassRefPtr<U>& b)
{
    return a == b.get();
}

template <typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, const RawPtr<U>& b)
{
    return a.get() == b.get();
}

template <typename T, typename U> inline bool operator==(const RawPtr<T>& a, const PassRefPtr<U>& b)
{
    return a.get() == b.get();
}

template <typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, const PassRefPtr<U>& b)
{
    return a.get() != b.get();
}

template <typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, const RefPtr<U>& b)
{
    return a.get() != b.get();
}

template <typename T, typename U> inline bool operator!=(const RefPtr<T>& a, const PassRefPtr<U>& b)
{
    return a.get() != b.get();
}

template <typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, U* b)
{
    return a.get() != b;
}

template <typename T, typename U> inline bool operator!=(T* a, const PassRefPtr<U>& b)
{
    return a != b.get();
}

template <typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, const RawPtr<U>& b)
{
    return a.get() != b.get();
}

template <typename T, typename U> inline bool operator!=(const RawPtr<T>& a, const PassRefPtr<U>& b)
{
    return a.get() != b.get();
}

template <typename T> PassRefPtr<T> adoptRef(T* p)
{
    adopted(p);
    return PassRefPtr<T>(p, PassRefPtr<T>::AdoptRef);
}

template <typename T, typename U> inline PassRefPtr<T> static_pointer_cast(const PassRefPtr<U>& p)
{
    return adoptRef(static_cast<T*>(p.leakRef()));
}

template <typename T> inline T* getPtr(const PassRefPtr<T>& p)
{
    return p.get();
}

} // namespace WTF

using WTF::PassRefPtr;
using WTF::adoptRef;
using WTF::static_pointer_cast;

#endif // WTF_PassRefPtr_h
